Wire forms the basic building block of the world's electric power system, including transformers, transmission and distribution systems, and motors. The discovery of revolutionary HTS compounds in 1986 led to the development of a radically new type of wire for the power industry; this discovery is the most fundamental advance in wire technology in more than a century. However, to date only short samples of the HTS tape used in the manufacture of next-generation HTS wires have been fabricated at high performance levels. In order for HTS technology to become commercially viable for use in the power generation and distribution industry, it will be necessary to develop techniques for continuous, high-throughput production of HTS tape.
IBAD, such as is described in Neumüller et al., U.S. Pat. No. 6,258,472, dated Jul. 10, 2001, and entitled Product Having a Substrate of a Partially Stabilized Zirconium Oxide and a Buffer Layer of a Fully Stabilized Zirconium Oxide, and Process for its Production has shown great promise in creating desirable buffer layer characteristics as a support for a functional layer of a ceramic superconducting material, such as yttrium-barium-copper-oxide (YBCO) atop the buffering layers of yttrium-stabilized zirconia (YSZ) and cerium oxide (CeO2). During IBAD, a vacuum-deposition process that combines physical vapor deposition (PVD) with ion-beam bombardment occurs: a vapor of coating atoms is generated with an electron-beam evaporator and deposited on a substrate. Ions are simultaneously extracted from a plasma and accelerated into the growing PVD film at energies of several hundred to several thousand electronvolts (eV). The ions impart substantial energy to the coating and coating/substrate interface. This achieves the benefits of substrate heating (which generally provides a denser, more uniform film) without significantly heating the substrate material and degrading bulk properties. The ions also interact with the coating atoms, driving them into the substrate and producing a graded material interface, which enhances adhesion. These factors combine to allow the deposition of uniform, adherent, low-stress films of virtually any coating material on most substrates, including the buffer layers of HTS tapes. In addition, concurrent ion beam bombardment of a growing film has been shown to impart biaxial texture. IBAD has been specifically used for this purpose to achieve a high-degree of biaxial texture in materials used as buffer layers for HTS tapes.
While such prior art IBAD processes are well known for their rapid deposition rates, they are also prone to process variations. The high-throughput continuous deposition of buffer layers necessary to enable cost-effective and, consequently, widespread adaptation of HTS materials in the electricity transmission/distribution industry necessitates deposition runs that can take upwards of one week to complete, during which time process variations sufficiently severe to disrupt the process are likely to occur. HTS films are extremely sensitive to such variations in system parameters and conditions such as chamber pressure and temperature. As a result, prior art HTS materials have been successfully fabricated only on a small scale.
It is thus an object of this invention to provide a high-throughput IBAD system and method for its use that enables continuous deposition of high quality thin films such as the buffer layers of HTS tapes.